Efficient computation of hashes

The sequential computation of hashes at the core of many distributed storage systems and found, for example, in grid services can hinder efficiency in service quality and even pose security challenges that can only be addressed by the use of parallel hash tree modes. The main contributions of this paper are, first, the identification of several efficiency and security challenges posed by the use of sequential hash computation based on the Merkle-Damgard engine. In addition, alternatives for the parallel computation of hash trees are discussed, and a prototype for a new parallel implementation of the Keccak function, the SHA-3 winner, is introduced

Spatially resolved spectroscopy of monolayer graphene on SiO2

We have carried out scanning tunneling spectroscopy measurements on exfoliated monolayer graphene on SiO$_2$ to probe the correlation between its electronic and structural properties. Maps of the local density of states are characterized by electron and hole puddles that arise due to long range intravalley scattering from intrinsic ripples in graphene and random charged impurities. At low energy, we observe short range intervalley scattering which we attribute to lattice defects. Our results demonstrate that the electronic properties of graphene are influenced by intrinsic ripples, defects and the underlying SiO$_2$ substrate.Comment: 6 pages, 7 figures, extended versio

Possibility, Impossibility and Cheat-Sensitivity of Quantum Bit String Commitment

Unconditionally secure non-relativistic bit commitment is known to be impossible in both the classical and the quantum worlds. But when committing to a string of n bits at once, how far can we stretch the quantum limits? In this paper, we introduce a framework for quantum schemes where Alice commits a string of n bits to Bob in such a way that she can only cheat on a bits and Bob can learn at most b bits of information before the reveal phase. Our results are two-fold: we show by an explicit construction that in the traditional approach, where the reveal and guess probabilities form the security criteria, no good schemes can exist: a+b is at least n. If, however, we use a more liberal criterion of security, the accessible information, we construct schemes where a=4log n+O(1) and b=4, which is impossible classically. We furthermore present a cheat-sensitive quantum bit string commitment protocol for which we give an explicit tradeoff between Bob's ability to gain information about the committed string, and the probability of him being detected cheating.Comment: 10 pages, RevTex, 2 figure. v2: title change, cheat-sensitivity adde

Hyaluronic acid patellar peri-tentinous injection efficacy in sudden detrained rats

Introduzione L’attività fisica moderata seguita da improvvisa interruzione può influenzare le caratteristiche biologiche del tendine. Lo scopo del lavoro è stato quello di valutare l’attività cellulare, le caratteristiche istologiche, istomorfometriche e microstrutturali del tendine patellare e della sua entesi in condizioni di non allenamento (sedentarietà), allenamento ed improvviso arresto dell’attività fisica. E’ stato ipotizzato che un’iniezione peri-tendinea di acido ialuronico nelle settimane successive all’improvviso arresto dell’attività fisica potesse mantenere l’integrità strutturale e biologica del tendine patellare. Materiali e Metodi 24 ratti Sprague Dawley maschi di 8 settimane sono stati suddivisi in tre gruppi, allenati per 10 settimane, fino a 60-80% VO2max. I ratti sono stati suddivisi in tre gruppi: Non Allenati (6), Allenati (6), Disallenati (12). A 6 dei 12 ratti del gruppo Detrained, è stata praticata un’infiltrazione peri-tendinea a nel tendine patellare destro di 300 μl di acido ialuronico, mentre nei rimanenti 6, è stata praticata l’infiltrazione con soluzione fisiologica. I tendini rotulei espiantati sono stati valutati con coltura cellulare, valutazione biologica molecolare, valutazioni morfologiche microstrutturali, proliferazione, conta ed attività cellulare. Risultati I risultati in vitro hanno evidenziato vitalità e conta cellulare simili fra i Gruppi Trained e Detrained-HA con un incremento significativo del metabolismo cellulare rispetto agli altri Gruppi. La cellularità ha mostrato valori maggiori nei Gruppi Non Allenati e Detrained-NaCl ove si è osservata una biosintesi del collagene III superiore ai Gruppi Trained e Detrained-HA. Contrariamente, la produzione di collagene I e II presentava valori maggiori nei Gruppi Trained e Detrained-HA suggerendo una superiore efficienza tessutale e metabolica di questi ultimi. Conclusioni Questi risultati confermano che l’allenamento ed il suo improvviso arresto hanno effetti sulla struttura tendinea patellare di ratto e che l’iniezione peritendinea di acido ialuronico nel periodo di inattività ha effetti significativi su metabolismo cellulare e sul tendine rispetto al trattamento con soluzione fisiologica.Introduction Different conditions may alter tendon characteristics. Clinical evidence suggests that tendon injuries are more frequent in athletes that change type, intensity and duration of training. Aim of the study was the assessment of training and especially detraining on the patellar tendon (PT) and its enthesis. We also hypotized that peri-tendineous injection with Ialuronic acid in detrained rats could prevent structural tendon integrity. Materials and Methods: 24 male adult Sprague-Dawley rats were divided into 3 groups: 18 rats were trained on a treadmill for 10 weeks. Of these, 6 rats were euthanized immediately after training (trained group), 12 were caged without exercise for 4 weeks before being injected in peri patellar tendon tissue, 1 group with Ialuronic acid (de-trained HA group) and the other with Saline solution and then euthanized (de-trained Saline group). The remaining 6 rats used as controls (untrained rats). Patellar tendons were evaluated with cellular coltures, molecular biological evaluation, microstructural morphologic evaluation, cellular proliferation, cellular number and activity. Results In vitro results showed cells vitality and number similar between Trained and Detrained-HA groups with an increased significance cellular methabolism vs the others groups. Cellularity showed better values in Non Trained and Detrained-NaCl Groups where we saw superior collagen III biosinthesis vs Trained and Detrained-HA Groups. On the other side Collagen I and II showed better values in Trained and Detrained-HA suggesting a better tissue activity of Detrained-HA Group. Conclusion Sudden interruption of physical activity has a negative effect on tendons and peri-tendineous patellar injection with Ialuronic Acid can represent a protective tendon therapy after a sudden detraining period

Higher entropic uncertainty relations for anti-commuting observables

10.1063/1.2943685Journal of Mathematical Physics496

On Monotone Function Closure of Perfect and Statistical Zero-Knowledge

Assume we are given a language L with an honest verifier perfect zero-knowledge proof system. Assume also that the proof system is a 3 move Arthur-Merlin game. The class of such languages includes all random self-reducible language, and also any language with a perfect zero-knowledge non-interactive proof. We show that such a language satisfies a certain closure property, namely that languages constructed from L by applying certain monotone functions to statements on membership in L have perfect zero-knowledge proof systems. The new set of languages we can build includes L itself, but also for example languages consisting of n words of which at least t n are in L. A similar closure property is shown to hold for the complement of L and for statistical zero-knowledge. The property we need for the monotone functions used to build the new languages is that there are efficient secret sharing schemes for their associated access structures. This includes (but is not necessarily lim..